Plastic bag



11, 1964 R. H. MILNER ETAL 3,144,197

PLASTIC BAG Filed Feb. 20, 1963 SLEEVE IN OPEN POSITION SLEEVE m CLOSED POSlTlON- INVENTORS RICHARD H. MILNER HAROLD G. LIGHTFOOT THEIR ATTORNEY United States Patent 3,144,197 PLASTIC BAG Richard H. Milner, Knutsford, and Harold G. Lighttoot, Ashton-upon-Wersey, Sale, England, assignors to Shell Oil Company, New York, N.Y., a corporation of Delaware Filed Feb. 20, 1963, Ser. No. 260,072 Claims priority, application Great Britain Feb. 26, 1962 1 Claim. (Cl. 229-625) The present invention is concerned with bags and sacks (hereinafter referred to simply as bags) for the storage of particulate solids, e.g. powders, granules and nibs, particularly though in no way exclusively plastics, i.e. synthetic organic polymeric materials in granular form, e.g. polystyrene nibs.

The requirements of a bag for large-scale use for the storage of particulate solids include adequate strength; simplicity of manufacture and use; and if possible the ability to be used more than once. It has already been found that bags of adequate strength can be made from thermoplastic sheet material such, for example, as PVC (polyvinyl chloride) or polyethylene, e.g. by cutting off lengths of lay-fiat polyethylene tube and heat-sealing the open edges of each length to form in effect a plastic envelope. The main problems have arisen in the manufacture of such bags and in particular in the provision of means for filling the bags and the methods hitherto proposed involve the provision of a side-filling aperture located near the top edge of the bag. The provision of such an aperture adds appreciably to the initial cost of the bag since the aperture must be so positioned as not to impair the strength of the bag and some sort of baflle must be provided to prevent the contents of a filled bag from spilling out through the filling aperture. In the bags previously proposed a bafile in the form of an internal flap has been provided, the flap being of such size and location that it is pressed by the contents of a filled bag against the aperture in the bag and at the same time against part of the inside of the bag so as to seal said aperture when the bag is moved from the vertical position in which it is filled and turned on its side to distribute the contents throughout the volume of the bag. The provision of internal flaps adds to the cost of the bags in view of the more complicated fabrication operation needed during bag manufacture and since in practice it is not at all easy to open up the aperture again for emptying the bag, such bags are usually torn open and as a result they cannot be re-used. Moreover, if only part of the contents of a full bag is required, it is often not feasible to leave the remaining material in a bag which has been torn open in this way owing to the risk of accidental spillage and also contamination by the entry of dirt.

The present invention provides a bag for the storage of particulate solids in which access to the interior of the bag for filling and emptying purposes is provided by a flexible sleeve which is attached at one end to the bag and which encloses an aperture in the bag, the arrangement being such that after the bag has been filled with a predetermined quantity of a particulate solid said sleeve can be inserted through said aperture into the bag and flattened against the inner wall surface of the bag in which position said sleeve is held by the contents of the bag to seal the bag during subsequent handling.

The accompanying drawing illustrates a perspective view of a preferred embodiment of the invention.

Referring to the drawing, the bag 1 is preferably formed from a thermoplastic organic polymeric material (hereinafter referred to as thermoplastic polymer), e.g. polyethylene or PVC, in flexible sheet form, although it is also possible to form the bag from other flexible sheet material,

ice

e.g. kraft paper or a laminate of a thermoplastic polymer and a kratt paper or textile sheet. In its preferred form, as illustrated in the drawing, the bag is fabricated from thermoplastic polymer sheet, conveniently a piece of thinwalled tubing often referred to in the art as lay-flat tubing (although two separate sheets can also be used if desired), by heat-sealing adjacent free edges, as illustrated at 2, to gether in conventional manner. In the case of a bag formed from lay-flat tubing, heat-sealing is, of course, required to form only the two ends of the bag. In such case the heat'sealed edges will normally constitute the top and bottom edges of the bag and in forming a bag in accordance with the present invention from lay-flat tubing, heat-sealing of the edge which in the finished bag will constitute the top edge can be interrupted over part of its length to provide the above-mentioned aperture.

The sleeve, as designated by 3 in the drawing, is also preferably formed from a thermoplastic polymer in sheet form by heat-sealing together two separate sheets. Alternatively, the sleeve may be formed by employing a length of lay-flat tubing of appropriate size. The sleeve is conveniently attached to the bag by sealing the end of the sleeve into apertured portion 4 of the top edge of the bag during the operation of forming the top edge. Alternatively, the end of the sleeve can be placed round the aperture so as to overlie the edges of the bag which define said aperture and then heat-sealed to said edges. The material forming the sleeve should be sufficiently flexible to permit the sleeve to be pushed into the bag after filling and pulled out again when required. Advantageously, the outer surface of the sleeve (the inner surface contacts the inner wall surface of the bag when the sleeve is pushed into the bag to seal the bag) is provided with slightly raised portions, e.g. ribs or pressed-up portions 5, which allow air to escape form the bag during handling. For example, the sleeve can be formed from thermoplastic polymer sheet which has been (or is subsequently) embossed to form a regular pattern of raised and depressed portions on the surface. It will be appreciated that such embossing should not affect the flexibility of the sleeve to an extent which prevents the sleeve being readily inserted into and withdrawn from the bag. From this point of view it will usually be advantageous to form the sleeve from a more flexible, e.g. a thinner, sheet material than that used to form the bag itself. It will be appreciated that if desired the sleeve can be made from other forms of sheet material, e.g. kraft paper or thermoplastic polymer/kraft paper laminate.

A bag in accordance with the present invention will now be described by way of example.

The bag, of a size suflicient to contain, for example, 50 pounds of granulated polystyrene, is formed by cutting off a suitable length (e.g. 27 inches) of polyethylene tubing 42 inches in circumference and having a wall thickness of 0.01 inch and heat-sealing the open ends of the tubing together to form, respectively, the top and bottom edges of the bag. The sealing of the top edge is interrupted for about 6 inches to form an aperture midway along the top edge. One end of a 6-inch diameter polyethylene sleeve about 7-8 inches in length, which is also formed from lay-fiat polyethylene tubing of somewhat thinner wall thicknes than that used for the bag itself, is inserted into the aperture in the top edge and heat-sealed to the bag in such a manner that the only means of access to the interior of the bag is through the sleeve. It will be understood that the dimensions quoted are given by way of illustration and are in no way limitational.

When filling bags with solids in particle form as part of a manufacturing operation, e.g. in the manufacture of plastics, it is usual to feed the solid particles through a chute or downpipe into the bag and it will be realized that the sleeve portion of the bags formed in accordance with the present invention is particularly suitable for filling through a downpipe round the lower end of which the sleeve is fitted, e.g. pushed on, and clamped if required. After filling, the sleeve is removed from the downpipe and tucked into the bag in a position in which it lies against the inside wall of the bag. The bag is then laid flat on the floor and pressed down so that the contents occupy the whole volume of the bag, during which operation the sleeve becomes pressed against the bag to form an effective seal for the filling aperture. When it is desired to remove part or all of the contents of the bag,

the bag is placed in an upright position and the sleeve is pulled out to form a convenient means for directing the solid particles into, for example, a bin or hopper. If only part of the contents of the bag is required, the remainder can be left in the bag with less risk of contamination occurring than if the bag were torn open since the sleeve can be re-inserted into the bag to form an eflective closure.

If it is desired to seal the contents of the bag against atmospheric moisture, e.g. when storing black plastics, it is a simple matter to heat-seal the open end of a thermoplastic polymer sleeve after filling and to open up the end of the sleeve again before emptying the bag.

In a modification of the bag as just described, the sleeve is cut from embossed lay-fiat tubing so as to permit air to pass into and out of the bag after sealing; such an arrangement is not, of course, used when protection of the bags contents from atmospheric moisture is desired. It will be appreciated that bags of many different shapes and sizes can be made in accordance with the present invention and that, for example, the sleeve and/ or the bag itself can be made by joining separate pieces of sheet material, though in the case of polyethylene bags, for example, it is usually more convenient to start from lay-flat tubing. However, it is also possible to form the bag and sleeve in one piece by blow-molding a thermoplastic polymer such, for example, as polyethylene. The sleeve portion itself need not be cylindrical and in some cases a slight outward coning thereof may be advantageous from the point of view of ease of fitting to a filling downpipe. On the other hand, an inward coming of the sleeve may be found in some instances to make it easier to insert the sleeve in the bag. Also as previously indicated, the sleeve can be attached to the inside or to the outside of the bag and the bag and/ or sleeve can be made from any suitable sheet material, the joins being effected by heat-sealing Where appropriate or by some other bonding method, e.g. by using adhesives.

We claim as our invention:

A bag for the storage of particulate solids in which access to the interior of the bag for filling and emptying purposes comprises: a rectangular bag, a flexible, inwardconing sleeve formed from thermoplastic polymer sheet material and attached at the normally top end of the bag and enclosing an aperture in said bag, the arrangement being such that after the bag has been filled with a predetermined quantity of a particulate solid said sleeve can be easily inserted through said aperture into the bag and flattened against the inner wall surface of the bag in which position said sleeve is held by the contents of the bag to seal the bag during subsequent handling, the surface of said sleeve which is its outer surface when in position outside said bag being provided with slightly raised portions, whereby an air passage is defined when said sleeve is held in position inside said bag.

References Cited in the file of this patent UNITED STATES PATENTS 2,538,920 Shumann Jan. 23, 1951 3,051,605 Stannard Aug. 28, 1962 FOREIGN PATENTS 624,701 Canada Aug. 1, 1961 

